1. Field of the Invention
The present invention relates generally to semiconductor devices and particularly to semiconductor devices including a metal-insulator-metal (MIM) capacitor having a highly reliable storage node.
2. Description of the Background Art
As devices are highly integrated, chips are reduced in size and in semiconductor devices memory""s capacitor is arranged at reduced intervals and also reduced in size. Developing small-size DRAMs requires a capacitor having increased capacitance. Accordingly, an electrode is formed of ruthenium (Ru), a material of metal, and as the capacitor""s dielectric film a dielectric film of high permittivity such as Ta2O5 film is used in developing an MIM capacitor.
FIG. 33 is a plan view of a dynamic random access memory (DRAM) using a conventional cylindrical capacitor. FIG. 34 is a cross section taken along a line XXXIVxe2x80x94XXXIV of FIG. 33. This cross section is parallel to a bit line BL. In FIG. 33 on a silicon substrate 151 transfer gates TGs 101 are arranged with a predetermined pitch and bit lines BLs 102 are arranged orthogonal thereto also with a predetermined bitch. The intersecting transfer gates and bit lines form meshes each provided with landing pad of polysilicon 103. The bit line overlies a bit line contact 104.
In FIG. 34, a storage node contact (SC) interlayer insulation film 105 formed of boro-phospho tetra-ethyl-ortho-silicate (BPTEOS) film is penetrated by an SC barrier metal plug 114. SC interlayer insulation film 105 underlies a storage node (SN) interlayer insulation film 7 formed of BPTEOS film and penetrated by a storage node electrode 108 and a dielectric film 109 such as Ta2O5. Furthermore, dielectric film 109 is covered with and a cylinder is also filled with a cell plate 110 of a top electrode of a capacitor. Thereon a contact interlayer insulation film 111 formed of plasma TEOS film is stacked and furthermore an aluminum interconnection 112 and a passivation film 113 are formed.
The above conventional MIM capacitor is fabricated, as described hereinafter. With reference to FIG. 35, initially as SC interlayer insulation film 105 of BPTEOS film is vapor deposited to have a thickness of 450 nm and a photoresist pattern is used as a mask to pattern the BPTEOS film. Oxide film is then dry-etched. Then as a storage node contact""s (SC""s) barrier metal 114 TiN film is provided through chemical vapor deposition. The TiN film is then chemically mechanically polished to obtain the SC barrier metal having a cross section, as shown in FIG. 35.
Then as an SN interlayer insulation film a SiN film 115 is vapor deposited to have a thickness of 80 nm and so is BPTEOS film 107 to have a thickness of 1200 nm. Photoresist is then used as a mask to pattern the SN interlayer insulation film. Oxide film is then dry-etched to obtain a geometry, as shown in FIG. 36, which shows that an opening is provided for forming a storage node.
Sputtering is then employed to vapor deposit Ru to have a thickness of 20 nm and chemical vapor deposition is then employed to vapor deposit Ru. Thus in an SN hole Ru film 108 is uniformly vapor deposited to form a geometry of SN electrode film 108 (FIG. 37).
Ru film 108, which will serve as an SN electrode, and SN interlayer insulation film 107 are then chemically mechanically polished. Then as dielectric film 109 tantalum oxide (Ta2O5 film) is vapor deposited to have a thickness of 12 nm and then oxidized at 400xc2x0 C. in ozone (O3) gas and thus crystallized.
After the oxidization in ozone, as a cell plate (CP) electrode, Ru film 110 is vapor deposited to form the CP electrode. Then as CH interlayer insulation film 111 BPTEOS film is vapor deposited and then aluminum interconnection 112 is vapor deposited and patterned (FIG. 34). Then as passivation film 113 plasma nitride film is vapor deposited to form a conventional DRAM memory cell, as shown in FIG. 34.
As has been described above, the dielectric film of high permittivity used in the capacitor needs to be oxidized by oxygen, ozone or the like. In this oxidation step, ruthenium (Ru) and other similar metals are also oxidized. However, ruthenium oxide and other similar metal oxides are conductive and the capacitor does not have its capacitance impaired.
However, ruthenium (Ru) used as a material for an electrode of a capacitor provides poor contact with oxide film. As such, (a1) when vapor deposited Ru film 8 is chemically mechanically polished the Ru film has poor contact with BPTEOS film, resulting in the film peeling off disadvantageously. Furthermore, (a2) in ozone (O3) oxidization the Ru film forming SN electrode film 108 is oxidized and as a result BPTEOS film 107 forming the SN interlayer insulation film and Ru film 108 forming the SN electrode have poor contact therebetween and a gap may result. As such between the FIG. 37 condition and the FIG. 38 condition (a3) when the intermediate product is chemically mechanically polished, as described above, the cylindrical capacitor collapses. These disadvantages have been studied, as disclosed for example in Japanese Patent Laying-Open Nos. 2002-83880 and 2002-76302 and U.S. Pat. No. 6,146,941.
Furthermore as another disadvantage (a4) when ozone is used to oxidize the dielectric film an oxidizing species of the ozone reaches the TiN plug forming SC barrier metal 114. The plug is oxidized and thus has high resistance and a current leaks disadvantageously.
The present invention mainly contemplates a semiconductor device preventing a cylinder from collapsing at a bottom electrode of a capacitor in forming the capacitor. In addition the present invention in one aspect contemplates a semiconductor device capable of preventing oxidization of an interface of an SC barrier metal and a polycrystalline silicon plug and in another aspect contemplates a semiconductor device capable of reducing a current leaking from the capacitor.
In accordance with the present invention a semiconductor device includes: a first interlayer insulation film disposed on a semiconductor substrate; a second interlayer insulation film disposed on the first interlayer insulation film; and a cylindrical metal film penetrating the second interlayer insulation film, the cylindrical metal film having a bottom facing downward and exposed to the layer of the first interlayer insulation film, the cylindrical metal film having an opening, as seen downward, and extending from the second interlayer insulation film upward. Furthermore the present semiconductor device includes a storage node contact, in contact with the bottom of the cylindrical method film, disposed in the first interlayer insulation film, the storage node contact being recessed toward the bottom of the cylindrical metal film, the bottom having a protruding geometry embedded in the recess.
Thus the cylindrical metal film and the storage node contact can contact each other over an increased area to provide reduced contact resistance. Furthermore, the film and the contact that contact each other over the increased area allow the capacitor""s bottom electrode and the contact to contact each other closer to prevent the bottom electrode from collapsing.
In accordance with the present invention another semiconductor device includes: a first interlayer insulation film disposed on a semiconductor substrate; a second interlayer insulation film disposed on the first interlayer insulation film; an etching stopper film disposed in contact with an upper surface of the second interlayer insulation film; a cylindrical metal film penetrating the second interlayer insulation film and the etching stopper film, the cylindrical metal film having a cylindrical bottom facing downward and an opening facing upward, the cylindrical metal film extending from the etching stopper film upward; a storage node contact, in contact with the bottom of the cylindrical metal film, disposed in the first interlayer insulation film and a dielectric film covering a cylindrical inner surface of the cylindrical metal film and an outer surface of a portion protruding from the etching stopper film, the etching stopper film being SiN film vapor deposited at no more than 400xc2x0 C.
A portion lower than the etching stopper film can support the cylindrical metal film to prevent the capacitor""s bottom electrode from collapsing. Furthermore, the etching stopper film that is formed at a low temperature can protect the storage node contact from further crystallization and prevent the storage node contact from having increased contact resistance.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.